The popularity of both the Internet and digital technologies (e.g., compact disks “CDs” and digital versatile disks “DVDs”) has created tremendous problems for copyright owners of digital [media] content. The ability to reproduce, play and transmit digital content has become readily available to anyone with a personal computer and access to the Internet. This ability has led to widespread abuses to the rights of copyright owners who are unable to stop the illegal reproduction of their works.
One particular area where copyright ownership is particularly abused involves the music industry. The illicit pirating of digital music across the Internet is causing immeasurable damage to the music industry. Heretofore, most music content has been packaged and stored in an open, unsecured format that can be read and processed by any digital media player or recorder, i.e., content can be readily reproduced, stored and transmitted. To address this, the music industry has sought to create a secure domain to control the rampant pirating of music.
One solution the music industry is exploring involves establishing standards for secure playback and recording devices that process specially encoded content. Numerous secure devices and systems have been proposed. For instance, U.S. Pat. No. 5,513,260, issued on Apr. 30, 1996, entitled “Method and Apparatus For Copy Protection For Various Recording Media,” describes a system in which an authorization signature is required before a protected CD can be played. PCT application WO 99/60568, published on Nov. 25, 1999, entitled “Copy Protection Using Broken Modulation Rules,” also discloses various anti-pirating systems. Each of these references is hereby incorporated by reference.
In addition, a group referred to as SDMI (Secure Digital Music Initiative), made up of more than 180 companies and organizations representing information technology, consumer electronics, telecommunication, security technology, the worldwide recording industry, and Internet service providers, is attempting to develop standards and architectures for secure delivery of digital music in all forms. Information regarding SDMI can be found at their website at sdmi.org.
One of the challenges with implementing compliant systems, such as those sought under SDMI, is that various competing requirements must be met. For instance, under SDMI: (1) people must be allowed to make an unlimited number of personal copies of their CDs if in possession of the original CD; (2) SDMI-compliant players must be able to play music already in a library; (3) SDMI must provide the ability to prevent large numbers of illicit perfect digital copies of music; and (4) SDMI must prevent the illicit distribution on the Internet without any compensation to the creator or copyright holder. Thus, SDMI requires that a limited form of copying must be allowed, while at the same time widespread illicit copying must be prohibited.
Unfortunately, such competing requirements create opportunities for hackers and pirates to defeat the protection schemes of the systems. Accordingly, protection schemes that are difficult to defeat, but will meet the open requirements for initiatives such as SDMI, have and are being developed.
My co-pending, commonly assigned application Ser. No. 09/730,336, filed Dec. 5, 1999, incorporated herein by reference, discloses a method of and apparatus for imposing a degree of difficulty on illicitly copying digital media content. This application, as well as other prior art, discloses the use of watermarks for imposing a degree of difficulty on illicitly copying digital media content. The watermarks are in the form of coded digital signals interspersed during the process of putting the digital media content on a recording medium, such as a CD or DVD. Typically, the digital media content from the recording medium is partitioned into sections having fixed lengths from about 7 to 30 seconds dependent on the nature of the song recorded on the medium and the length of time required to decode the watermarks accurately. The watermarks are placed in the digital content with different coding and/or levels in different sections such that the effects of the watermarks are not perceptible to a typical listener of the digital content. The coding and/or levels of the watermarks are usually dispersed throughout a section and in some instances a watermark is repeated in a section. All sections or only some sections (e.g. only alternate sections) contain watermarks. The watermarks are designed to prevent illicit copying of the digital content because illicitly copied and modified digital content from the Internet or a CD or DVD onto a recording medium, such as a CD or a hard disk of a personal computer, does not include a correct and/or complete sequence of such watermarks. Playback devices responsive to the copied digital content are equipped with signal processors which prevent readout of at least a portion of the digital content which does not include the correct sequence of such watermarks. Typical modification of the content of illicit copying includes compression (e.g. MP3) or truncation (e.g. only a song is copied from a CD, not the entire medium).
Legally importing watermarked music into a protected (i.e. secure) domain (e.g. a copyrighted song having SDMI watermarked coding on a CD, DVD or the Internet) involves encrypting the content and attaching some copyright management (policy) information, describing the rights and capabilities of the user. A consortium, e.g. SDMI, controls what encryption is used in the protected domain, how playback is controlled, what the user can do with the music, the format of the policy file etc.
For example, music is typically delivered on audio CDs including a collection of tracks or songs. Illicit copying of such CDs is often limited to a small subset of the songs on a particular CD. In my previously mentioned application, such illicit copying is made considerably more difficult because a complete collection of tracks and watermarks must be present before a portion of an audio CD can be reproduced.
Watermark detection is a statistical process, that is not 100 percent accurate and requires substantial computational resources (digital signal processing). In a protected domain, there is no need for watermark detection, so devices having lower computational ability can play back the music. However, only legally purchased music should be allowed to be imported into the protected domain. If watermark protected music is illicitly manipulated (compressed or extracted from a protected domain), a hacker who cuts the watermark protected music into short pieces can import that music into the protected domain, piece by piece. This is because the watermark based copy protection does not work for pieces of music or sections that are shorter than a certain length (e.g. 7 seconds).
I realized that a possible way of illicitly importing watermarked digital content to a secure domain from a partial, illicit copy of an original CD or from the Internet is to import to the secure domain short sections of the digital content; the sections are so short (e.g. less than seven seconds) that none of the sections have enough information for reliable detection of the watermarks embedded in them. In such a situation, the prior art recording and/or playback devices would be incapable of determining that the digital signal it is processing contains digital content which is to be protected from illicit importing to a secure domain.
If such a short section or segment can be imported in one recording session an attacker, i.e., hacker, who desires to make an illicit copy might store the digital content one section at a time. The hacker restarts importing until he succeeds, for example, in the average once every ten times. Then the hacker resets the recording equipment and starts importing the next section of the digital content. By the time the hacker has imported the last section of the digital content, i.e., the portion of the digital content between the last watermark and the end of the digital content, he would have spent about 10 times as long as he would have spent if he had imported the original (unprotected) entire digital content. For many hackers, the time required to produce such a recording would be an acceptable price for illicitly copying the entire digital content, for example, to make a master CD of a musical composition for illicit sale. Upon completion, the hacker has individual sections which he would merge together to form the illicit copy of the digital content.
It is, accordingly, an object of the present invention to provide a new and improved method of and apparatus for preventing illicit importing to a secure domain of digital content protected by watermarks.
Another object of the invention is to provide a new and improved method of and apparatus for further increasing the difficulty of importing to a secure domain digital content including spaced watermarks which impose a degree of difficulty on illicitly copying the digital content.
An additional object of the invention is to provide a new and improved method of and apparatus for preventing illicit importing to a secure domain of digital content protected by spaced watermarks, despite attempts by hackers to defeat the protection provided by the spaced watermarks by removing all the watermarks.